Semiconductor nanostructures, nanoagglomerates, and nanowires have attracted considerable attention because of their potential applications in mesoscopic research, the development of nanodevices, and the potential application of large surface area structures. For several decades, the vapor-liquid-solid (VLS) process, where gold particles act as a mediating solvent on a silicon substrate forming a molten alloy, has been applied to the generation of silicon whiskers. The diameter of the whisker is established by the diameter of the liquid alloy droplet at its tip. The VLS reaction generally leads to the growth of silicon whiskers epitaxially in the <111> direction on single crystal silicon <111> substrates. In addition, laser ablation techniques have been performed on metal-containing (iron or gold) silicon targets, producing bulk quantities of silicon nanowires. Further, thermal techniques have been used to produce a jumble of silicon dioxide (SiO2) coated crystalline nanowires that have their axes parallel to the <112> direction. Further, these nanowires are deficient because of twinning, high order grain boundaries, and stacking faults.
Recently, national lab researchers, in an effort to begin an ongoing dialogue to forecast the direction of environmental science and technology, ranked the top ten environmental technology breakthroughs for 2008. Not surprisingly, molecular design is expected to play an important role in the development of advanced materials. Included in this framework is the design of nano-assembled and non-stoichiometric catalysts designed for the efficient control of chemical processes.
Heterogeneous catalysts are typically prepared by decorating high surface area solids such as silica or alumina with active metals or metal ions from precursor materials such as cation complexes [Mn+ Lm-x](n-xm), anion complexes (e.g., [Pt4+ F6]2-), or neutrals such as copper (II) acetylacetonate (Cu(AcAc)2). These processes typically use starting reagents and produce products that are harmful to the environment (e.g. solvents, metal halides, strong acids, or other environmentally aggressive reagents and or products). A high-surface-area support is needed to provide the proper dispersion of the active ingredients so that the high intrinsic activity of these catalytic metals or ions can be realized in practice. Without this support, many catalytic agents show very little active surface area. Often, the intrinsic catalytic activity of the supported metals or metal ions is changed by interaction with the support metal ions or oxygen atoms. Thus, some supports are not benign towards the catalytic agents. Moreover, the catalytic properties of these agents are often compromised as a result of the efforts to synthesize supported catalysts having high dispersions of the active ingredient. These uniquely assembled catalysts might then be used to more efficiently control combustion processes and reactions such as hydrocarbon reforming.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.